This application claims benefit of priority under 35 U.S.C. xc2xa7119 to Japanese Patent Application No.2001-233986, filed on Aug. 1, 2001, the entire contents of which are incorporated by reference herein.
1. Field of the Invention
The present invention relates to an implant for bone connector used for connecting bones, and more particularly, to an implant for bone connector having a connecting portion with which various connecting members are engaged.
2. Description of the Related Art
When connecting bones such as thoracic vertebrae or lumbar vertebrae, the following method has been conventionally employed. A first implant 3 is screwed into centrum 1 such as the thoracic vertebra and the lumbar vertebra. A second implant 4 is screwed into centrum 2. A connecting rod 5 connects the first implant 3 to the second implant 4 as shown in FIG. 1.
The first implant 3 includes a screw portion and a head portion. The screw portion is screwed into centrum and the head portion with a large diameter has a rod engaging groove. Also, the second implant 4 includes the same conformation. Since end portions of the connecting rod 5 are fixed to the rod engaging groove of the first implant 3 and that of the second implant 4 respectively, the connecting rod 5 is integrally fixed to the first implant 3 and the second implant 4 and accordingly a bone connector is formed.
Further, an implant 9 is screwed into centrum 10 separating from the centrum 1 and the centrum 2 for hooking one end of a connecting member 7 such as an artificial ligament. A hook portion 9F is provided on an upper portion of the implant 9, and one end portion of the connecting member 7 is hooked over the hook portion 9F. Another end portion of the connecting member 7 is hooked over a hook portion 5F provided on one top end (the side engaged the first implant 3) of the connection rod 5.
Also, instead of using the connecting rod 5, the connecting member 7 may be used for connecting a first implant to a second implant. A first implant having a hook portion is screwed into the centrum 1, a second implant having a hook portion is screwed into the centrum 2, and both end portions of the connecting member 7 are hooked over the hook portion of the first implant and that of the second implant respectively.
According to the above-described method screwing the implant for bone connector into the centrum for fixing a positional relation between vertebrae, it is necessary to precisely screw the implant into the centrum without damaging other portion. This method requires high technique and a burden of the centrum becomes large, because the implant is screwed into centrum.
The present invention has been proposed in view of the above-described circumstances, and it is an object of the present invention to provide an implant for bone connector capable of being stably fixed to a vertebral arch of a vertebra without damaging the centrum and to various connecting members.
In order to achieve the above object, the present invention provides an implant for bone connector comprising: a fixing clamp to support a vertebral arch of a vertebra by grasping the vertebral arch; an implant body provided on an upper portion of the fixing clamp; a connecting portion provided to an upper portion of the implant body for engaging a connecting member which connects the implant with another implant; and a movable clamp provided to the implant body and disposed to be opposed to the fixing clamp for grasping the vertebral arch.
According to the present invention, the fixing clamp is provided to a lower portion of the implant body, and supports the vertebral arch of the vertebra by grasping the vertebral arch. The connecting portion is provided on the upper portion of the implant body, and the connecting member is engaged with the connecting portion. The movable clamp is provided to the implant body, is disposed to be opposed to the fixing clamp, and grasps the vertebral arch. Therefore, the implant can grasp the vertebral arch from both sides of the vertebral arch by means of the fixing clamp and the movable clamp, and is engaged with the connecting member. As a result, it is possible to stably fix the implant to the vertebral arch without damaging the centrum, and the implant can be used in the same manner as the conventional implant.
In a preferred embodiment of the present invention, the fixing clamp has a curved shape.
According to the embodiment, even if the fixing clamp has a curved shape, the fixing clamp can be engaged with the vertebral arch. Therefore, it is possible to stable fix the implant to the vertebral arch without damaging the centrum.
In a preferred embodiment of the present invention, the movable clamp can be moved and adjusted in a direction approaching the fixing clamp and separating from the fixing clamp.
According to the embodiment, since the movable clamp can be moved freely in accordance with a size of the vertebral arch, the implant can strongly grasp the vertebral arch from both sides of the vertebral arch by means of the fixing clamp and the movable clamp, and be stably fixed to the vertebral arch.
In a preferred embodiment of the present invention, the movable clamp has a curved shape.
According to the embodiment, even if the movable clamp has a curved shape, the movable clamp can be engaged with the vertebral arch. Therefore, it is possible to stably fix the implant to the vertebral arch without damaging the centrum.
In a preferred embodiment of the present invention, the connecting portion has a rod engaging groove, with a female thread portion, through which the connecting member passes, and has an engaging groove, with a female thread portion, through which the movable clamp passes.
According to the embodiment, it is possible to fix the connecting member and the movable clamp to the connecting portion by means of detent screws.